Investigation of sound field uniformity for multisourced traveling wave tube

Acoustic environment test has to be completed in the ground to ensure the reliability and life for satellites and other aerospace structures in space. Traveling wave tubes (TWT) are often adopted to. achieve required acoustic environment in the ground attributed to its high sound intensity in the tube. However, the distortion and nonlinearity caused by large amplitude acoustic wave propagation make it difficult to control the noise spectrum accurately and maintain the uniform acoustic field distribution. In this paper, numerical simulation based on Comsol Mutiphysics software is developed to investigate three-dimensional large amplitude sound wave propagation and the acoustic field uniformity in the tube. The sound sources are applied separately or together at the center frequency of 1/3 octave frequency spectrum in order to demonstrate the acoustic field uniformity in different operating conditions. Moreover, energy superposition of acoustic field generated by each sound source at each center frequency is completed to calculate the acoustic field distribution in the tube. The boundary impedance at the end is fixed according to the corresponding experimental conditions and numerical simulation results are consistent with acoustic waveguide theory. Multiple sources can improve acoustic field uniformity substantially in the traveling wave tube and the contribution of each source to sound pressure level of specific field points is different.